Solids/liquids separator

ABSTRACT

A separator for separating solids and other objects (debris) from a liquid, and having a separator body ( 2 ) through which the liquid, having debris entrained therein ( 16, 19, 20 ), flows from an inlet ( 6 ) to an outlet ( 13 ), and a port ( 5 ) for diverting flow from the outlet during moderate flows whereby the debris entrained in the liquid is removed. A floor ( 11 ) wherein the separator is raised to form a hump ( 43 ) adjacent to or in which the opening ( 5 ) is located.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/276,278,filed Nov. 12, 2002, and issued as U.S. Pat. No. 6,868,971 on Mar. 22,2005, which is the National Stage of International Application No.PCT/AU01/00543, filed May 11, 2001, which claims priority to AustralianApplication No. PQ 74666, filed May 12, 2000. The aforementionedapplications are hereby incorporated herein by reference in theirentirety.

TECHNICAL FIELD

This invention relates to a solids/liquid separator, and moreparticularly the invention relates to a separator for separatingpollutant solids and other objects (debris) from a liquid, such as in astormwater drainage system. Such separators are also known as pollutanttraps, and any reference to a solids/liquid separator, also includespollutant traps.

BACKGROUND ART

In stormwater drainage systems, it is desirable to remove debris fromthe storm water before it is discharged into rivers, lakes, bays and thelike. Floating debris can be a particular problem because it accumulateson the banks of rivers and shores of bays while heavier debris sinks tothe bed smothering aquatic life and causing siltation.

Consequently these materials can badly degrade the environment.Unfortunately, due to sociological problems such debris now includessyringes which obviously represent a further public health risk problem.It is desirable therefore to try to remove debris from stormwater andthis is usually accomplished by means of separator or pollutant trapsthat basically attempt to trap debris from stormwater by use of meshes,grates or the like. Unless these are specially configured they tend toclog up, thereby reducing their effectiveness. Another problem inremoving debris from stormwater is that energy is lost from the flow andmanifests itself as raised water levels upstream of the trap withpossible local flooding. Present pollutant traps use walls and the likeacross the pipeline as a means of diverting the flow into the separator.As these obstruct the pipeline they can cause backing up during highflows raising upstream water levels and causing local flooding. If theyare not regularly cleaned out, as is often the case, the accumulationsof debris and litter can build up and block the pipeline with similarresults.

An object of the invention is to provide a separator that largelyovercomes the problems noted above. The separator of the invention mayfind application in other areas where it is necessary to separate debrisfrom liquids such as in sewage systems, trade waste treatment or townwater supplies.

DISCLOSURE OF THE INVENTION

According to the present invention there is provided a separator forseparating solids and other objects from a liquid, said separator havinga separator body through which the liquid, having debris entrainedtherein, flows from an inlet to an outlet, and means for diverting flowfrom the outlet during moderate flows whereby the solids and otherobjects entrained in the liquid is removed, and wherein the means fordiverting the flow is an opening in the separator and has adjacentthereto a wall containing a plurality of apertures therethrough.

Preferably the separator is for separating both floating and heavierbodies from the flow.

Preferably the opening is in an internal floor of the separator.

Preferably the separator body includes an upstream conduit portion and afirst chamber the floor of which is level with the bottom of the saidconduit. The opening noted above is located in this floor. In analternative arrangement of the invention, portion of the said floor israised to form a hump adjacent to which the said opening is located.

Preferably the separator includes a second chamber located eitherlaterally to, or on both sides of, the first chamber and also extendingbeneath it, there being said opening and apertured wall between thefirst and second chambers through which the liquid, together with theentrained debris is diverted.

Preferably the liquid level in the second chamber is kept below thefloor level of the first chamber by means of a secondary conduitconnected to the second chamber and to the conduit at a downstream pointbeing at a lower level than the upstream conduit portion.

In two of the alternative arrangements described hereinafter, thesecondary conduit is contained within the second chamber.

Preferably the above-mentioned opening has two sides extending down tothat portion of the apertured wall immediately below the opening.

Preferably the second chamber contains the perforated wall interposedbetween the flow and the secondary conduit for deflecting the solids andother objects from the flow.

Preferably the floor of the second chamber is located below that of thefirst chamber so as to provide a holding area for heavier solids andother objects.

Flow into the second chamber takes place through the above mentionedopening although if this exceeds the capacity of the secondary conduit,portion of the liquid will flow over the opening and leave the separatorthrough the downstream conduit portion connected to the first chamber.This conduit may be at the same, or in an alternative arrangement of theinvention, at a lower level than the upstream conduit portion.

BRIEF DESCRIPTION OF THE DRAWINGS

A number of preferred embodiments of the invention will now be describedwith reference to the accompanying drawings, in which:

FIG. 1 is a schematic longitudinal cross-sectional side elevational viewof a first embodiment of the separator of the invention,

FIG. 2 is a schematic cross-sectional plan view of the separator of FIG.1 of the drawings,

FIG. 3 is a cross-sectional side view taken along line A-A of FIG. 1,

FIG. 4 is an enlarged view of portion of the separator of FIG. 1,

FIG. 5 is a simplified hydrographic analysis of the flow characteristicsof the preferred embodiments of the invention,

FIG. 6 is a schematic longitudinal cross-sectional side elevational viewof a second embodiment of the separator of the invention,

FIG. 7 is a schematic cross-sectional plan view of the separator of FIG.6 with some constructional features omitted for the sake of clarity,

FIG. 8 is a cross-sectional view taken along line B-B of FIG. 6,

FIG. 9 is a schematic longitudinal cross-sectional side elevational viewof a third preferred embodiment of the invention,

FIG. 10 is a schematic cross-sectional plan view of the separator ofFIG. 9 of the drawings,

FIG. 11 is a cross-sectional view taken along line C-C of FIG. 10 of thedrawings,

FIG. 12 is a schematic longitudinal cross-sectional side elevationalview of a fourth preferred embodiment of the invention,

FIG. 13 is a schematic cross-sectional plan view of the separator ofFIG. 12,

FIG. 14 is a cross-sectional view taken along line D-D of FIG. 13,

FIG. 15 is a schematic cross-sectional plan view of a modified versionof the embodiment of FIGS. 12 to 14,

FIG. 16 is a schematic longitudinal cross-sectional side elevationalview of a fifth preferred embodiment of the invention,

FIG. 17 is a schematic plan view of the separator of FIG. 16,

FIG. 18 is a schematic cross-sectional view taken along line E-E of FIG.17,

FIG. 19 is a schematic cross-sectional view taken along line F-F of FIG.17,

FIG. 20 is a schematic longitudinal cross-sectional side elevationalview of a modified version of the embodiment of FIGS. 16 to 19, and

FIG. 21 is a schematic cross-sectional view taken along line G-G of FIG.20.

BEST MODES OF CARRYING OUT THE INVENTION

The separator in FIGS. 1 to 4 is constructed to remove debris, such assolids and other objects, from storm water drainage pipes. The separatorincludes a separator body 2 containing a diversion chamber 3 andseparator/holding chamber 4 which can also capture oils, tars and otherscum. Fluid thereafter flows through an opening 5 with downwardprojecting sides 14 and an apertured (perforated) curved wall 9, as bestseen in FIG. 4, and firstly through an inlet conduit 6, and thereinafterthrough an outlet conduit 7 and secondary outlet conduit assembly 8.

The separator body 2 is preferably cast from concrete although the bodymay also be formed from materials other than concrete.

The conduits 6 and 7 are typically already in service and the overalllength of the separator is the same as the nominal length of pipes in astormwater drain (typically 2.4 m). In this way the separator of theinvention may be retrofitted in a stormwater drain by removing one ofthe pipes and replacing it with the separator of the invention.

Diversion chamber 3 is separated from separator/holding chamber 4 by awall 10 that extends from the top of the separator 17 to a floor 11, byfloor 11 and by common walls 24 and 26. This is best seen in FIGS. 1 and2. The diversion chamber 3 includes an inlet port 12 and an outlet port13 that provide liquid communication with the conduits 6 and 7. Thediversion chamber 3 also includes an opening 5 located in the upstreamsection of the floor 11 and provides liquid communication withseparator/holding chamber 4. The opening 5 has sides 14 that projectdown to perforated wall 9 and so direct liquid 18 into separator/holdingchamber 4. This is best seen in FIGS. 1 and 3. The purpose of sides 14are to retain floating bodies 16 in separator/holding chamber 4 on watersurface 15, after they have been propelled through the opening 5 anddown perforated wall 9 by the force of the incoming liquid 18 enteringinlet port 12 from conduit 6.

Heavier bodies 19, 20 are propelled down the perforated wall 9 by theliquid 18. A non-perforated V-shaped central section 25 of the wall 9extending downwards to static water level 15 prevents heavier bodies 20from lodging in the openings 22 of the perforated wall. This is bestseen in FIG. 3. The heavy bodies 20 move transversely toseparator/holding chamber 4, settling out on the floor 21 from wherethey can later be removed by pumping.

In the present preferred arrangement, the curved perforated wall 9extends the width of the separator/holding chamber 3 and is enclosed bythe walls 26 and a wall 41, as well as the floor 21 beneath as seen inFIG. 3. Experience may indicate other orientations, positions andopenings of the wall.

In the preferred arrangement, the openings 22 through the curvedperforated wall 9 over the face 23 of which liquid 18 containing debris19 and 20, passes are best seen in FIG. 4. The openings 22 allow theliquid 18 and solids 19, being smaller than the openings 22 to passwhile the bodies 20 larger than the openings 22 move down the face 23 ofthe wall 9 and onto the floor 21 of the separator for later removal,such as by pumping. In moving down face 23, bodies 20 also abrade theface and will tend to dislodge any adhering material.

The orientation of the openings 22 and the violent agitation in what isknown as “hydraulic jump” indicated as 44, and caused by the impact ofrapidly flowing liquid 18 on liquid surface 15 adjacent to the face 23of the perforated wall, will tend to dislodge floating bodies 16 andheavier bodies 20 and move them away from the face 23 of the wall andinto the adjacent section of chamber 4 so that the wall is self-cleaningand the perforations therethrough do not become obstructed by thebuild-up of solids. The greater the flow in conduit 6, the higher thevelocity of liquid 18 and hence the agitation and self cleaning effectson perforated wall 9 at liquid level 15. This, as referred topreviously, is technically known as a “hydraulic jump” and occurs whenrapid flow is caused to change to tranquil flow with violent agitationand consequent loss of energy. The liquid 18 passes through theperforations 22 in the wall and flows to the secondary conduit 8 via avertical pipe 27 that has its inlet 28 at the floor 21 so that solids 19can be scoured by the liquid 18. The top of the pipe 27 is open andlocated above the level of conduit 6 to facilitate inspection andcleaning. A removable cap 42 seals the top of the pipe.

Secondary conduit 8 has its upstream invert 29 below the level of thefloor 11, as can be seen in FIG. 1. Typically this distance is at least200 mm. As will be seen from the figure the invert level 29 of secondaryconduit 8 determines the static level of liquid level 15.

Secondary conduit 8 is generally parallel to conduit 7 but laid at aflat grade so that on reaching a junction pit 31 the inverts of bothpipes are at the same level 30. Stormwater drainage pipes have typicalgrades of between 1 in 60 to 1 in 100 so that a drop of 200 mm from theinvert of inlet 12 to the static liquid level 15 would require thelength of the secondary conduit 8 to be of 12 and 20 metresrespectively.

The diameter of secondary conduit 8 is related to but less than that ofconduit 7, typically ranging from 100 mm to 300 mm. Situations may arisewhere larger sizes are needed. For example, where conduit 7 is of largediameter or to obtain a higher treatment efficiency, as described below.

When the separator is installed within a drainage system, junction pit31 may be an existing pit. If the separator is near the downstream endof a system discharging stormwater to an open water body, the downstreamend of secondary conduit 8 may terminate at a head-wall.

The separator has lids 33 enclosing its top 17 to prevent unauthorisedentry and/or to prevent odours or insect breeding. The lids 33 may beremoved for inspection, maintenance and cleaning purposes.

When the flow 18 increases to such a rate as to equal the capacityflow-rate of secondary conduit 8, the liquid level 15 rises in chamber 3to the level of floor 11. During flows greater than the capacityflow-rate of secondary conduit 8 the liquid level 15 rises above thelevel of floor 11 and the excess liquid 32 passes through outlet 13 anddown conduit 7 to junction pit 31 and beyond. When excess liquid flow 32occurs in conduit 7 the depths of flow in the separator and junction pit31 will be similar in accordance with the principles of pipe flow. Hencethe difference in depths between the two said locations remains similarensuring that the flow in secondary conduit 8 also is kept relativelyconstant. Hence excessive flow through opening 5 that could causeundesirable agitation, with possible loss of trapped solid bodies inseparator/holding chamber 4 through opening 5, is avoided.

The passage of stormwater runoff in a pipeline can be graphicallyrepresented to facilitate understanding and analysis. One method isshown in FIG. 5 in which a simple triangular shape represents the changein flow-rate past a point with time and is known as a flood hydrograph.The area under the triangular hydrograph represents the volume of floodrunoff while the apex of the triangle represents the maximum flow-rate.It will be seen that as a storm progresses, the flow-rate of waterthrough the separator increases to a maximum and then slowly recedes. Ifthe flow capacity of the secondary conduit 8 is represented by thehorizontal line drawn through the hydrograph, then the area below theline represents the volume of stormwater that is treated and then passesdown conduit 8, while the area above the line represents the excessvolume that passes over opening 5 and down conduit 7 and so is nottreated. This method provides an acceptably accurate estimate of thevolume of flow treated. It can be adjusted to meet water authorityspecifications by changing the capacity of secondary conduit 8 byvarying either its' diameter, slope or length or any combination ofthese three factors.

In a similar manner, the size of the openings 22 in perforated wall 9can chosen to prevent a specified minimum size of heavier solid 20 frompassing through the wall and so be retained in separator/holding chamber4.

In a second alternative embodiment of the invention, seen in FIGS. 6, 7and 8, the secondary conduit 8 is laid inside conduit 7 betweenseparator 2 and downstream pit 31 and so obviates the need to excavate atrench in which to lay secondary conduit 8 as required in the firstembodiment. As shown in FIG. 6, in this embodiment the conduit 8functions as a siphon as its obvert 34 is now above the upstream invert29 of conduit 7.

For secondary conduit 8 to siphon liquid from chamber 4, all trapped airmust be first removed from it. This is achieved by air bleed line 35connected to secondary conduit 8 at high point 36 and to a fixed nozzle37 at inlet port 12. The nozzle is aligned in the direction of incomingflow 18.

The downstream end of secondary conduit 8 terminates in vertical bend 38extending into a hole 40 excavated below floor 41 of pit 31. This holeis filled with liquid from low flows in conduit 7 and so seals off end38, preventing air from entering secondary conduit 8 at this location.

When flow occurs in conduit 6, the velocity of the falling liquid 18scavenges air from nozzle 37 which in turn draws air from the secondaryconduit 8 via the air bleed line 35. This process removes all air fromthe secondary conduit 8 and flow commences under the siphonic actionwith liquid being drawn into the conduit at end 39 in chamber 4, beneathperforated wall 9 and discharges through end 38 in downstream pit 31.The flow capacity of conduit 7 is only slightly reduced by locatingsecondary conduit 8 within it as both conduits contribute to carryingthe total flow.

In a third alternative embodiment of the invention seen in FIGS. 9, 10and 11, the secondary conduit terminates within the body 2 with itsinvert 30 at the same level as the invert of outlet port 13. Floor 11now slopes from the invert level of inlet port 12 to the invert ofoutlet port 13 and contains the end of secondary conduit 8. Body 2 isnow of circular cross-section and, in FIG. 10, the diversion chamber 3is shown centrally disposed with respect to the body although thechamber may be disposed to one side of the body.

This embodiment of the separator of the invention could be employedwhere the conduits 6 and 7 have yet to be laid so that the separatorcould be first installed and then the conduits 6 and 7 subsequently laidto it. By this means the length of conduit 8 is minimised, so reducingthe cost of the installation.

In a fourth embodiment of the invention shown in FIGS. 12, 13 and 14,the floor 11 is raised in its central section to form a hump 43 so thatthe rapid flowing liquid 18 flows up the hump and drops into opening 5for treatment. The hump is typically between 200 and 500 mm high withrespect to the conduit 6 invert. Secondary conduit 8 is arranged in asimilar manner to that in the above third embodiment of the invention.

In this fourth arrangement, opening 5 may be widened in a directiontransverse to that of the conduit 6 so that a greater portion of theflow from conduit 6 than in other embodiments of the invention, dropsthrough the opening before the liquid level 15 rises to the top of theopening 5 in hump 43. The diameter of secondary conduit 8 may also begreater in order to carry this flow. When the liquid level 15 risesabove floor level 11 in hump 43, excess liquid 32 moves past opening 5and down hump 43 to pass out of the body 2 through outlet port 13 andinto conduit 7.

This arrangement is made possible because flow in pipelines occurs asrapid or super-critical flow, even at quite moderate flow rates. Thusthe flow will move up and over hump 43 at high flow rates insuper-critical mode. Provided the flow is not induced to change to thesub-critical flow mode by means of “hydraulic jump”, no energy lossoccurs. This means that no backing up of flow in conduit 6 will occurwhen the pipe flow is full as it will be in super-critical mode.Therefore the possibility of local flooding upstream is avoided.

However, at low flow rates the liquid 18 will bank up behind the hump43, which will then act as a weir. While floating bodies 16 may passover the weir, heavier bodies 19 and 20 will not and may sink to theinvert of conduit 6. These bodies 19 and 20 must be periodically removedif obstructions to flow 18 in conduit 6 are to be avoided and this isachieved when super-critical flow occurs.

As flow increases in conduit 6, as occurs during a storm, the flow modein the conduit changes from sub-critical to super-critical flow atrelatively low flow rates. The super-critical, or rapid flow 18, impactson the banked up water, or tranquil water, forming the “hydraulic jump”.As the flow rate increases, the “hydraulic jump” moves downstreamtowards the hump and the super-critical flow behind it scours theheavier bodies 19 and 20 from the invert of the conduit.

When the flow is sufficiently high, the “hydraulic jump” moves up thehump 43 and the following super-critical flow carries the heavier bodies19 and 20 up the hump 43 and into opening 5. This arrangement of theinvention can be designed so that the required flow occurs with asufficient frequency to avoid blocking of the conduit 6 with the heavierbodies 19 and 20.

Very low, or “trickle flows”, in conduit 6 can pass directly intoholding chamber 4 through inclined slots 44 in the side walls of chamber3 adjacent to the upstream end of hump 43. The slots have their lowerends level with the invert of conduit 6. The slots are cleaned duringhigh flow by the scavenging action of super-critical flow.

An important feature of those embodiments of the present invention thatinvolve the use of a hump is that if the holding chambers 4 becomefilled with debris, litter and other matter, the flow 18 together withthe entrained materials will pass over hump 43 and into outlet port 13and conduit 7 thus bypassing the separator. Where heavier bodies 20settle out in conduit 6 they will be removed during periods ofsuper-critical flow over the hump. Consequently there will not be abuild-up of materials that could lead to blockage of conduit 6 and thesubsequent possibility of upstream flooding.

In a modified form of the fourth embodiment of the invention, as seen inFIG. 15, the mode of operation is essentially the same as in the fourthembodiment but conduits 6 and 7 are now disposed to one side of theseparator together with diversion chamber 3. In this modified embodimentthe approach and reverse slopes of hump 43 are splayed on one side onlyand the opening 5 is in liquid communication with holding chamber 4 onthe splayed side of the hump only.

This modified embodiment can apply where the pipeline is located behindthe kerb line of a street, as is usually the case, and designed to avoidfouling other services that are also located behind the kerb line, andthe holding chamber is therefore located under the roadway and this isconvenient for inspection and cleaning operations.

The separators of the embodiments of FIGS. 16 to 21 are constructed butnot restricted, to removing debris from small storm water drainagepipes, whilst these embodiments can also prove effective in capturingoils, tars and other scum. In these embodiments a circular separatorbody 100 incorporates a diversion/bypass chamber 102 (first chamber) andseparator/holding chamber 103 (second chamber), together with inlet portand conduit 104 and outlet port and conduit 105.

The circular separator body 100 is preferably formed from concretealthough, once again, other materials, other than concrete, may be used.

The conduits 104 and 105 are typically already in service and theoverall length of the separator is once again the same as the nominallength of pipes in a storm-water drain (typically 2.4 m). In this waythe separator of the invention could once again be retrofitted in astorm-water drain by removing one of the pipes and replacing it with theseparator of this preferred embodiment of the invention.

Diversion/bypass chamber 102 is enclosed within separator/holdingchamber 103 and has its floor 106 at the same level as inverts 107 and108 of the inlet and outlet conduits respectively. Floor 106 extends thefull length of separator body 100. A transverse hump 109 extends thefull width of the floor and is located near its upstream end. This isbest seen in FIG. 16. Downstream of the hump the floor is bounded onboth sides by low return weirs 110 and 111, the crests of which arebelow the crest of the hump. Several small notches 112 in the weirsextend to floor 106.

Baffle walls 113 and 114 are located immediately behind and parallel tothe weirs and extend longitudinally from the ends of the hump to theoutlet port and conduit 105. Lower edges 115 of the baffles extendbeneath the level of floor 106. Upper edges 117 of the baffles extend tothe top of the separator body 100.

Screens of vertical wires 118 are attached to the lower edges 115 andextend beneath floor 106, as best seen in FIG. 16. The spacing of thewires is set to retain a specified size of bodies 123. The ends of thescreens beneath hump 109 are connected by screen wall 119 while thedownstream ends finish flush with separator body 100. The bottom edgesof screen walls 118 and 119 are attached to horizontal screen 126 toform an enclosed cage.

The two principal modes of operation of these preferred embodiments ofthe invention will be described with reference to the FIGS. 16 to 21.

In the first mode of operation the depth 120 of flow 121 enteringdiversion/bypass chamber 102 through inlet port 104 is less than that ofthe height of the hump 109. Consequently flow 121 together withentrained floating bodies 122 and heavy bodies 123 are diverted toeither side of floor 106 by the hump into separator/holding chamber 103via diversion ports 128.

Floating bodies 122 move towards the downstream end of the chamber wherethey are retained behind baffles 113 and 114.

Within the chamber, heavy bodies 123 tend to settle to floor 124although the slower settling of these bodies is drawn by flow 121towards the screen 118. Any of the bodies that reach screen 118 areintercepted by it and settle to the floor of chamber 103.

Flow 121 passes beneath the lower baffle edges 115 and over weirs 110and 111 to the floor 106 in chamber 102 and exits separator body 100 viaoutlet port and conduit 105.

The purpose of the weirs is to evenly distribute flow 121 through screen118 and so reduce its velocity to prevent any of the bodies obstructingthe screen. When flow 121 is very small it passes through the notches112 in the said weirs. This is to ensure that no flow containing bodies122 and 123 is held in inlet conduit 104 where these could settle and soobstruct the conduit.

The second principal mode of operation occurs when flow 121 passes overhump 109 in a phenomenon known as super-critical flow and practicallyall of flow 121 bypasses chamber 103. Super-critical flow occurs in allstorm-water drainage pipelines once a certain low flow is exceeded.

In the first mode of operation as the flow 121 increases, it banks up ashump 109 diverts it via diversion ports 128, to the chamber 103 fortreatment prior to passing over the weirs 110 and 111. Upstream in inletconduit 104, incoming super-critical flow impacts on the banked up flow121 forming once again a “hydraulic jump” in which the flow changes fromsuper-critical to sub-critical flow with some loss of energy.

As flow 121 further increases, the “hydraulic jump” progressesdownstream in conduit 104, into diversion/bypass chamber 102, over hump109 and exits separator body 100 via outlet port and conduit 105 beforedissipating and returning to super-critical flow in conduit 105.

At this, and greater, rates of flow in chamber 102 there is a tendencyfor the super-critical flow to scavenge liquid and captured matter fromchamber 103 via diversion ports 128 so that the latter should beespecially designed to prevent this occurring.

From observation of the impact of a jet of liquid on a flat plateinclined to the jet it is seen that the impacted jet forms a fan shapeon moving up the screen. Thus the flow displays both longitudinal andlateral velocity components.

From a consideration of the principle of conservation of mass it can beshown that the velocity of the lateral flow components are identical tothat of the impacting jet and to that of the flow component moving upthe plate. From this it follows that as the velocity of the jetincreases then so do the velocities of the component flows over theplate.

Further, as the inclination of the plate to the direction of travel ofthe jet is increased, the flow component up the plate decreases whilethe lateral flow components increase forming a more open fan shape.

This principle is employed in these embodiments of the invention whenthe supercritical flow impacts on the forward face of the hump 109.While most of the flow moves up the hump some moves laterally. As thediversion ports 128 are located adjacent to and on the forward face ofthe hump, as best seen in FIG. 16, the lateral flow components of theflow on the hump pass through the said ports and into chamber 103 thuspreventing the occurrence of the aforesaid scavenging flow. Thehorizontal floors of the said diversion ports are level with floor 106and extend into chamber 103. The horizontal roofs of the ports are abovethe level of the hump crest and parallel to the said floor while theenclosing sides are vertical so that the whole form short tunnelsproviding liquid communication between the said chambers. While thedownstream sides are at right angles to the hump, the upstream sides maybe inclined so that the tunnels may narrow towards their exits tochamber 103. The floating bodies 122 and heavier bodies 123 can beperiodically removed by opening a lid 125 and pumping out the contentsof separating/holding chamber 103.

In the second variation of this embodiment of the invention the bafflewalls 113 and 114 and screens 118, 119 and 126 are omitted. Instead, twosemi-circular baskets, constructed from perforated metal plate, areplaced in separator/holding chamber 103 on either side ofdiversion/bypass chamber 102. Each basket is the same size in plan asthe two semi-circular water surfaces of separator/holding chamber 103.The tops of the baskets extend up to the top of separator body 100 whilethe bottom of the baskets may rest on a floor 124. Thus when flow 121enters the chamber through holes in the perforated plate matching theshape of diversion ports 128 and aligned with them, bodies 122 and 123are retained in the baskets while flow 121 passes through theperforations in the diametrical side of the baskets, over weirs 110 andinto diversion/bypass chamber 102 to pass out of the separator viaoutlet conduit 105.

To clean out the separator of this varied embodiment, a lid 125 isremoved, the baskets are lifted out and bodies 122 and 123 emptied intoa truck for transport and disposal. The baskets are then hosed down toclean off any attached materials and then lowered into chamber 103 andthe lid 125 replaced.

In a further embodiment of the invention, shown in FIGS. 20 and 21, theinlet and outlet conduits are offset to one side of separator body 100so that there is only one diversion port 128, weir 110, baffle 113 andfull-depth screen 118 attached to baffle lower edge 115. The walls 129and 130 of diversion/bypass chamber 102 extend from floor level 106 tothe top 117 of the said separator body.

Diversion port 128 extends from wall 129 to baffle 113, and providesliquid communication between diversion/bypass chamber 102 andseparator/holding chamber 103.

In a further variation of this embodiment of the invention, the weir 110is located on the opposite side of chamber 102 to that described above.This confers the added advantage of distributing the flow more evenlythrough the vertical screen 118 since weir 110 is now further removedfrom the screen. In this variation the baffle 113 and the screen can nowbe adjacent to, or form part of, the sidewall 129 of chamber 102 whilethe conduits 104 and 105 must now be located some distance away from thewall of the body 100 to permit the flow to reach weir 110.

In an additional variation of this further embodiment and the furthervariation, the baffle wall 113 and screen 118 are omitted and arectangular basket fabricated from perforated plate is placed in theseparator holding chamber 103 and acts in the same manner as describedabove for the semi-circular baskets of the second variation of thatembodiment.

The modes of operation of this variation of the embodiment of theinvention are essentially the same that described in the preferredembodiment of FIGS. 16 to 19.

1. A separator for separating solids and other objects from a liquid,said separator comprising: a separator body through which the liquid,having debris entrained therein, flows from an inlet to an outlet, andmeans for diverting flow from the outlet during moderate flows wherebythe solids and other objects entrained in the liquid is removed, andwherein the means for diverting the flow is an opening in the separator,the opening having two sides extending down to a downwardly extendingcurved wall containing a plurality of apertures therethrough, andwherein at low flow the liquid acquires potential energy that isconverted to velocity energy as it falls by gravity through the openingand down the apertured wall to impact on the water surface in a lowerchamber causing violent agitation against the said apertured wall, thusmaintaining the apertures free of blockages by solid bodies.
 2. Theseparator as claimed in claim 1, wherein the opening is in an internalfloor of the separator.
 3. The separator as claimed in claim 1, whereinthe separator body includes an upstream conduit portion and a firstchamber the floor of which is level with the bottom of the said conduitand said opening is located in said floor.
 4. The separator as claimedin claim 3, wherein a portion of said floor is raised to form a humpadjacent to which the said opening is located.
 5. The separator asclaimed in claim 3, wherein the separator includes a second chamberlocated either laterally to, or on both sides of, the first chamber andalso extending beneath it, said opening being between the first andsecond chambers.
 6. The separator as claimed in claim 5, wherein theliquid level in the second chamber is kept below the floor level of thefirst chamber by means of a secondary conduit connected to the secondchamber and to a conduit at a downstream point being at a lower levelthan an upstream conduit.
 7. The separator as claimed in claim 6,wherein the secondary conduit is contained within the second chamber. 8.The separator as claimed in claim 5, wherein the second chamber containsthe apertured wall interposed between the flow and the secondary conduitfor deflecting the solids and other objects from the flow.
 9. Theseparator as claimed in claim 5, wherein the floor of the second chamberis located below that of the first chamber so as to provide a holdingarea for heavier solids and other objects.
 10. The separator as claimedin claim 5, wherein the liquid, together with the entrained bodies, isdiverted to the second chamber via diversion ports in the walls of saidfirst chamber.
 11. The separator as claimed in claim 5, wherein theliquid level in the second chamber is kept above the floor level of thefirst chamber by means of one or more weirs.
 12. The separator asclaimed in claim 11, wherein said weirs have notches in them toaccommodate lower liquid flow.
 13. The separator as claimed in claim 11,wherein said weirs have crests that are lower than the crest of saidhump.
 14. The separator as claimed in claim 11, wherein said secondchamber contains baffle plates parallel to the weirs but locatedlaterally therefrom, and extend from the said hump to the outlet port,with the lower edges of the baffles being below the floor of the firstchamber in order to retain floating solids and other objects.
 15. Theseparator as claimed in claim 14, wherein said apertured wall is formedby one or more vertical screens attached to the lower edge of eachbaffle with, the or their, lower edges connected to a respectivehorizontal screen whereby to form one or more enclosures.
 16. Theseparator as claimed in claim 15, wherein the, or each, said horizontalscreen allows heavier solids and other objects that passes through theone or more vertical screens to pass through into the second chamber.